Coin box telephone circuit



Jan. 3, 1967 E. M. HEIRBAUT COIN BOX TELEPHONE CIRCUIT Filed May 9. 1963SC [LQ/ 5C2 1 A If g? Y W IC CE gf F/GS g, 0 53 dc c5 5 w i A CC C lnvenor 2 CC MHE/RB AUT' Attorne United States Patent Office 3,296,375Patented Jan. 3, 1967 3,296,375 COIN BOX TELEPHONE CIRCUIT Edmond MarieHeirbaut, Antwerp, Belgium, assignor to International Standard ElectricCorporation, New York, N.Y., a corporation of Delaware Filed May 9,1963, Ser. No. 279,166 Claims priority, application Netherlands, May 16,1962, 278,487 3 Claims. (Cl. 179-65) The present invention relates to apay stations and more particularly to coin box telephone circuits whichare connected to a telephone exchange via a telephone line.

Coin box telephone circuits generally include a dial contact, a coincontact in parallel with the dial contact with a collectingelectromagnet which is operated by a reversal of the polarity of saidtelephone line. Such coin box telephone circuits are well known. In wellknown coin box telephone circuits a series connection of the said dialcontact and a collecting relay bridges said coin contact which is abreak contact. Hence, the dial contact is short circuited except when acoin has been inserted in the coin box. While the dial isshort-circuited, a dialling operation remains ineffective.

It has been found that the reversal of line polarity may accidentallyhappen during a dialling operation. Due to this the collectingelectromagnet is energized, the coin is collected and the coin breakcontact is closed thus, practically short-circuiting the dial contact.In this case, further dialling will remain without effect. This isobviously an undesirable situation.

It is therefore an object of the present invention to provide a coin boxtelephone circuit of the above type wherein the dialling operation isprevented from being disturbed by a polarity reversal of the telephoneline.

A related object of this invention is to provide means for preventingsaid dial contact from being short-circuited before a dialling operationis finished.

A further object of this invention is to provide means for branching thedial contacts in said telephone line in series with a parallelconnection of said collecting electromagnet and a first diode which isconductive for the normal line polarity, and that the series connectionof said coin contact which is a break contact and a second diode whichis conductive for the normal line polarity is coupled in parallel withsaid dial contact.

In accordance with one embodiment of this invention the coin boxtelephone circuit is characterized by the fact that the-dial contact isin parallel with the break contact of the coin contact which is achange-over contact and that a series circuit is branched across saidtelephone line, said series circuit being constituted by the makecontact of the coin change-over contact, said collecting electromagnet,a diode which is conductive for the reversed line polarity and a gravityswitch break contact which is closed when the handset of the subset isin its rest position.

The above mentioned and other objects and features of the invention willbecome more apparent and the invention itself will be best understood byreferring to the following description of embodiments taken inconjunction with the accompanying drawings in which:

FIG. 1 is a schematic diagram of a first embodiment of a coin boxtelephone circuit according to the present invention;

FIG. 2 shows a part of a second embodiment of the present coin boxtelephone circuit;

FIG. 3 represents a part of a third embodiment of the present coin boxtelephone circuit;

FIG. 4 shows a part of a fourth embodiment of a coin box telephonecircuit.

FIG. 5 represents a part of a fifth embodiment of a coin box telephonecircuit.

Referring to FIG. 1 there is shown a coin box telephone circuit whereinthe reversal of the telephone line polarity occurs when a calledsubscriber answers.

This coin box circuit is connected to a telephone exchange via thetelephone line a, b and includes the receiver Re, the transmitter Tr,the induction coil Ic the ringer R,, the capacitor C, the dial contactsdc, and dc and the hook switch make contacts s6 and sc All theseelements are interconnected in the usual manner which is therefore notdescribed in detail. The present invention is only concerned with thatpart of the coin box circuit shown at the right and below the dashedline.

The dial contact dc is branched in the telephone line in series with theparallel connection of a collecting electromagnet CE and a diode d,which is conductive for the normal line polarity, i.e., the conductors aand b at a positive and negative potential respectively. On the otherhand, the dial contact dc, is connected in parallel with the seriesconnection of a coin contact cc which is a break contact and a diode dwhich is also conductive for the normal line polarity.

The operation of this coin box telephone circuit is as follows. When thehandset is removed the hook switch make contacts so, and sc are closedand the calling subscriber receives dialling tone via the closed hookswitch make contact sc the induction coil 10,, the transmitter Tr, thedial contact dc in parallel with the diode d and the coin break contactcc, and the diode L1,. The required fee is then inserted in the coinbox. Responsive thereto the coin break contacts cc open thus removingthe short-circuit from the dial contact dc so that dialling is possible.The current then fiows from a to b via the closed hook switch makecontacts s0 the induction coil 1a,, the transmitter Tr, the dial Contactdc, and the diode 51,. It should be noted that the collectingelectromagnet CE cannot be energized due to its winding beingshortcircuited by the conductive diode d If after dialling the calledsubscriber does not answer, the fee will be mechanically returned in anot shown but well known manner. However, when the called subscriberanswers the polarity of the telephone line a, b is reversed in theexchange, so that the collecting electromagnet CE is energized asfollows: conductor b, winding of electromagnet CE, dial contact dctransmitter Tr, induction coil I0 closed hook switch make contact scconductor a.

Responsive to the electromagnet CE being operated, the fee is collectedand the coin break contact cc is closed again.

If the line polarity is reversed before the d alling operation isfinished, the collecting electromagnet CE is operated and the coin breakcontact cc is closed again. However, the dialling operation will not bedisturbed due to the presence of the diode d which is not conductive forthe reversed line polarity.

In the above described coin box telephone circuit the collectingelectromagnet CE is only released when the handset is returned to itsrest position. This means that the Winding of this electromagnet isincluded in the path followed by the speech current, so that itconstitutes a small damping element during the whole conversation. Inorder to remove such a drawback a diode d which is conductive for thereversed line polarity may be connected between the cathodes of thediodes al and d In this manner, when the fee has been collected, andhence when the coin contact cc is again closed, the speech current mayflow from conductor b to conductor a via diode d coin break contact cc,dial contact dc transmitter Tr, induction coil I0 closed gravity switchmake contact sc The winding of the collecting electromagnet is thusshort-circuited so the electromagnet is released.

Instead of connecting the coin break contact cc between thes anode ofthe diode d and the cathode of the diode d it may also be connectedbetween the cathodes of the diodes d and d This is shown in FIG. 2. Inthis case, however, a diode, such as diode d cannot be used forshort-circuiting the electromagnet CE after the reversed polarity hasbeen applied to the line.

Referring now to FIG. 3 therein is shown a part of a coin box telephonecircuit wherein the reversal of the telephone line polarity occurs whenthe handset is returned to its rest position. In this coin box the dialcontact dc is branched in the telephone line in parallel with the breakcontact of a coin contact cc which is a change-over contact. A seriescircuit is further branched across the telephone line a, b. It isconstituted by the make contact of the coin box changeover contact cc,the winding of the collecting electromagnet CE, the diode 03.; and thegravity switch break contact s which is closed when the handset is inits rest position. The diode d., is conductive for the reversed linepolarity.

This operation of this coin box circuit is as follows. When the handsetis removed the gravity switch make contacts s0 and sc are closed,whereas the gravity break contact s0 is opened. The calling subscriberreceives dialling tone via the closed gravity switch make contact s0 theinduction coil 1C the transmitter Tr and the dial contact dc in parallelwith the coin break contact. The required fee is then inserted due towhich the coin change-over contact cc moves to its work position thus,removing the short-circuit from the dial contact dc Dialling is thusmade possible. The speech current then flows from conductor a toconductor b via the closed gravity switch make contact s0 the inductioncoil I0 the transmitter Tr and the dial contact dc It should be notedthat the collecting electromagnet CE cannot be energized due to thegravity switch break contact 50 being open.

When the conversation is finished the calling subscriber brings thehandset back in itsrest position, thus opening the make contacts sc andsc and closing the break contact M The polarity of the telephone line,a, b is then reversed in the exchange, so that the collectingelectromagnet CE is energized as follows: conductor b, coin change-overcontact cc in its work position, winding of electromagnet SE, diode dclosed gravity switch break contact sc conductor a.

Since the collecting electromagnet CE can only be operated afterconversation, due to the presence of the contact sc it is clear that adialling operation can never be disturbed by a line polarity reversal.

Refenring to FIG. 4 there is shown a coin box telephone circuit whereinthe fee may be collected after the called subscriber has answered orafter the handset has been brought back in its rest position. Thiscircuit only diifers from that of FIG. 3 by the absence of the gravityswitch break contact .90 and by the presence of the diode d in the linein series with dial contact dc When the line polarity is reversed uponthe called subscriber answering the collecting electromagnet isenergized by the current which flows as follows: conductor .b, coinchange-over contact cc in its work position, winding of electromagnetCE, diode d conductor a.

The diode d is necessary in order to prevent current flow from conductorb to conductor a via the dial contact dc the transmitter Tr, theinduction coil I0 and the closed gravity switch makes contact sc Sincethe impedance of the latter circuit is smaller than that of the circuitincluding the electromagnet CE, the latter electromagnet would not beoperated.

When the line polarity is reversed after the handset has been broughtback in its rest position, the collectin-g electromagnet is energized inthe same manner as in the preceding case. However, the diode d does notplay a role since the gravity switch make contacts are open.

Although the coin box telephone circuit just described can beuniversally used, it should be noted that the dialling operation may bedisturbed by a polarity reversal of the telephone line due to theabsence of the gravity switch break contact s0 Referring to FIG. 5 thereis shown another coin box telephone circuit wherein the fee is collectedafter the called subscriber has answered and by means of which a callcan be made to some subscribers without inserting a fee.

When the handset is removed the gravity switch make contacts sc and s0are closed and the calling subscriber receives dialling tone via dc andd In the case a paid call has to be made, the required fee is insertedin the coin box due to which the coin make contact cc is closed. Thenumber of the subscriber to be called is then dialled and when thissubscriber answers the polarity of the telephone line a, b is reversedin the exchange so that the collecting electromagnet CE is energized asfollows: conductor b, closed coin make contact cc, diode d winding ofthe collecting electromagnet CE, dial contact dc transmitter Tr,induction coil 10,, closed gravity switch make contact sc conductor a.

Due to the electromagnet CE being operated, the fee is collected and themake contact cc of this electromagnet is closed and mechanically locked.The coin make contact cc is opened again so that the collectingelectromagnet CE is released. The speech current now flows via theclosed make contact ce. The dial contact dc is short-circuited by theclosed make contact cc which is only released when the handset isbrought in its rest position so that only then another call can be made.

Apparently, it would be sutficient to branch the make contact ce inparallel with the coin contact cc. However, in this case it would bepossible to make non paid calls to any subscriber after a single paidcall has been made. Indeed, when the handset is not brought back to itsrest position, the speech path remains closed via the closed makecontact cc and the closed gravity switch make contacts, Whereas, thedial contact is not short-circuited.

In the present circuit, when the number of a subscriber is dialled towhich only paid calls can be made and when the required fee has not beeninserted the coin make contact cc will remain open so that upon thecalled subscriber answering the polarity of the telephone line isreversed. Since the diode d is not conductive for this polarity theconnection will then be interrupted.

In the case a non paid call is made to a subscriber to which only suchcalls may be made the operation is the same as with a normal telephonesubset since the line polarity will not be reversed upon the calledsubscriber answering. The conversation current is then able to flowviadial contact dc and diode d While the principles of the inventionhave been described above in connection with specific apparatus, it isto be clearly understood that this description is made only by way ofexample and not as a limitation on the scope of the invention.

What is claimed is:

1. A coin box telephone circuit connected to a telephone exchange via atelephone line comprising a dial contact, a coin contact openedresponsive to a deposited coin and connected in parallel with said dialcontact, to prevent dialling before depositing a coin, a collectingelectromagnet coupled in series with said parallel connection andoperated responsive to a reversal of the polarity of said telephone lineto close said coin contacts and means independent of the operation ofsaid collecting electromagnet for preventing said dial contact frombeing short-circuited by said coin contacts before dialling iscompleted.

2. In the coin box telephone circuit of claim 1, wherein said dialcontact is in said telephone line in series With a parallel connectioncomprising said collecting electromagnet bridging a first diode which isconductive for the normal line polarity and, a second diode in seriesWith said coin contact, said series contact of said second diode andsaid coin contact bridging said dial contact, said second diode isconductive for the normal line polarity.

3. A coin box telephone circuit connected to a telephone exchange via atelephone line, said circuit comprising a dial contact in said line, acoin contact operated to an open condition responsive to a depositedcoin and connected to normally short out said dial contact to preventdialing before the deposit of a coin, a collecting electromagnetoperated responsive to a reversal of polarity of said telephone line toclose said coin contact, means for connecting said dial contact inseries With said collecting electromagnet, first diode conductive withthe normal line polarity bridging said collecting electromagnet, seconddiode conductive with the normal line polarity connected in series withsaid coin contact across said dial contact, third diode conductive forreversed line polarity connected between the junction point of saidsecond 'diode and said coin contact and the junction point of saidcollecting electromagnet and line whereby for the reversed polarity ofsaid line said Winding is short-circuited by the series connection ofsaid third diode and said coin contact.

References Cited by the Examiner UNITED STATES PATENTS 1,349,373 8/1920Erickson 17-6.5 2,066,391 1/1937 Collins et a1 1796.5 2,583,783 1/1952LornaX et a1. 179-63 KATHLEEN H. CLAFFY, Primary Examiner.

H. ZELLER, Assistant Examiner.

1. A COIN BOX TELEPHONE CIRCUIT CONNECTED TO A TELEPHONE EXCHANGE VIA ATELEPHONE LINE COMPRISING A DIAL CONTACT, A COIN CONTACT OPENEDRESPONSIVE TO A DEPOSITED COIN AND CONNECTED IN PARALLEL WITH SAID DIALCONTACT, TO PREVENT DIALLING BEFORE DEPOSITING A COIN, A COLLECTINGELECTROMAGNET COUPLED IN SERIES WITH SAID PARALLEL CONNECTION ANDOPERATED RESPONSIVE TO A REVERSAL OF THE POLARITY OF SAID TELEPHONE LINETO CLOSE SAID COIN CONTACTS AND MEANS INDEPENDENT OF THE OPERATION OFSAID COLLECTING ELECTROMAGNET FOR PREVENTING SAID DIAL CONTACT FROMBEING SHORT-CIRCUITED BY SAID COIN CONTACTS BEFORE DIALLING ISCOMPLETED.